Change of Occupancy - Insulate Existing CMU exterior walls?

[Meadowbend99]

Existing CMU storage building, was used as a bus barn for many years, will now be used for classrooms. I've specified adding insulation R-5.7 ci all along the exterior CMU walls, we are zone 2. They don't have the funds for it and would like to see if they can avoid it. We have to comply with 2015 IECC. For existing buildings, they can not be less conforming than what they were before. Before, it used an older hvac system (less efficient) and lighting was very outdated. They'll be installing much more efficient hvac and LED lighting, filling in spaces where overhead doors were located with CMU, and punch out in 2 spaces for new man doors. My best guess is it will be about the same as before, maybe a little more since they will be conditioning the whole space vs. half the space before. The codes talk about when the wall cavities are exposed they need to meet the requirements, but CMU is always exposed.

Can anyone help me find a clear statement on how to proceed? Thank you!

 

[steveray]

If the building is going to use any more energy, full compliance is required...You need to prove it wont...Lighting wattage has to comply...

C505.1 General. Spaces undergoing a change in occupancy
that would result in an increase in demand for either fossil
fuel or electrical energy shall comply with this code. Where
the use in a space changes from one use in Table C405.4.2(1)
or C405.4.2(2) to another use in Table C405.4.2(1) or
C405.4.2(2), the installed lighting wattage shall comply with
Section C405.4.

 

[Meadowbend99]

I was looking at that one. I don't know how they would be able to prove it. The building hasn't been "used" for decades. I doubt they would have records of bills that far back. It's full of old school fluorescent lighting and the HVAC condenser unit is long gone. Remnants of the furnace and rigid ducts remain. They're planning to use heat pumps and all LED lighting. Since it'll be classrooms they'll have computers and smart boards running all day.

 

[mtlogcabin]

C402.2.2 Above-grade walls.
The minimum thermal resistance (R-value) of materials installed in the wall cavity between framing members and continuously on the walls shall be as specified in Table C402.1.3, based on framing type and construction materials used in the wall assembly. The R-value of integral insulation installed in concrete masonry units shall not be used in determining compliance with Table C402.1.3 except as otherwise noted in the table. In determining compliance with Table C402.1.4, the use of the U-factor of concrete masonry units with integral insulation shall be permitted.

“Mass walls” where used as a component in the thermal envelope of a building shall comply with one of the following:

1. Weigh not less than 35 pounds per square foot (171 kg/m2) of wall surface area.

2. Weigh not less than 25 pounds per square foot (122 kg/m2) of wall surface area where the material weight is not more than 120 pcf (1900 kg/m3).

3. Have a heat capacity exceeding 7 Btu/ft2 • º;F (144 kJ/m2 • K).

4. Have a heat capacity exceeding 5 Btu/ft2 • º;F (103 kJ/m2 • K), where the material weight is not more than 120 pcf (1900 kg/m3).

 

[steveray]

I was looking at that one. I don't know how they would be able to prove it. The building hasn't been "used" for decades. I doubt they would have records of bills that far back. It's full of old school fluorescent lighting and the HVAC condenser unit is long gone. Remnants of the furnace and rigid ducts remain. They're planning to use heat pumps and all LED lighting. Since it'll be classrooms they'll have computers and smart boards running all day.

If it is close I would let their design professional certify it....

 

[Builder Bob]

Use COMCHECK to see if the trade offs in HVAC system and LEDS lights allow the building to "PASS" the energy codes for your state. The issue with the energy code book is that is generally prescriptive and does not allow tradeoffs to comply with the energy code.

Check with the local AHJ to see if COMCHECK is acceptable method for determination of energy code compliance.